This invention relates to the field of fiber optic networks and, more specifically, to devices to position optical elements for directing signals in fiber optic networks.
In fiber optic networks, light signals are transmitted along optical fibers to transfer information from one location to another. Optical switches are used to selectively couple light from an input fiber to an output fiber. Optical fibers typically have very small cross-sections and narrow acceptance angles within which light entering the fiber must fall to promote efficient propagation of the light along the fiber. As such, optical switches must transfer light with precise alignment.
One type of electromechanical optical switch operates by moving the ends of an input fiber relative to the ends of the output fiber. One problem with such an electromechanical switch is that the fibers themselves may be thin and subject to breakage if not properly protected. Reinforcing the fibers with stiff protective sheaths, however, makes the fiber less flexible. This increases the force required to manipulate each fiber into alignment and, thus, necessitates more power to operate the optical switch. In addition, with switches that accommodate a large number of input and output fibers, the complexity of maintaining accurate alignment for each optic path greatly increases the cost of the switch.
Another type of electromechanical switch operates by moving a mirror while maintaining the optic fibers and optical pathway stationary. In response to electrical signals, a relay arm moves a mirror into and out of an optical pathway. The relay arm moves the mirror substantially parallel to its reflective surfaces. The travel of the relay arm along that axis is limited by stops that determine the position of the mirror. The relay arm is constrained at the stops by only a single contact point.
One problem with such a switch is that the relay mechanism may not be able to provide the accuracy and precision in positioning the mirror that may be required by some optical switching networks. Accuracy is the ability to achieve a desired position with any given movement. Precision is the ability to repeatedly achieve the same position over a number of movements, regardless of where that position is located. Because the movement of the relay arm is constrained by only a single point of contact with the stopper, the switch may only be able to provide accurate alignment along a single axis (in the direction of the arm""s movement). The use of a single contact point may result in position inaccuracies due to the freedom of the relay arm to rotate about additional axis. Furthermore, relay mechanisms are typically constructed of materials that may be susceptible to significant wear from component contact through repeated use. Such material wear may lead to problems with precision placement of the mirror over time, in addition to the position inaccuracies.
Another problem with electromechanical switches is that they use a large electromechanical actuator that may not permit the placement of mirrors in the packing density that may be required for multiple switch arrays.
Other types of systems use electromagnetic actuators, for example, disk drive systems. These systems typically use actuators to position drive components over different regions of a disk. One problem with such electromagnetic actuators is that they require a control servo loop in order to operate. With a servo loop, the position of a component must be actively adjusted to maintain proper positioning. As such, actuators of this type are unable to repeatedly return components to the same position when actuated, without the use of an active control loop. This adds complexity to a system""s design and, thereby, may undesirably increase its cost.
The present invention pertains to an actuator that includes a shuttle, a stopper, and a motor coupled to the shuttle. The motor may be used to drive the shuttle against the stopper at a second position. The stopper may inhibit the rotation of the shuttle about a plurality of axes.